Thermalboard Compared to
Concrete Slab

A concrete slab is a very old method for delivering radiant heat. The chief advantage is that the slab is part of building structure, thus a large part of the radiant delivery system is paid for.

Issues to Consider


Thermalboard is more efficient that a concrete slab due to less resistance and better heat transfer characteristics, as shown in lower supply water temperature data below.


  • Response: A slab system works but is very slow to respond, creating significant control complications. It can not heat up rapidly or discharge quickly
  • Control: Setting your thermostat to one temperature and leaving it there for the heating system is no longer an option in modern, energy efficient homes.
  • Insulation: A minimum of R-10 insulation under the slab and sides are required unless you want to pay for years of thermal leakage.
  • Options: Due to the above issue’s engineers will sometimes specify an independent structural slab, then specify on top of the concrete a thermally isolated, quick responding and more energy efficient assembly such as Thermalboard… as you see on the right above.


Concrete Slab:

Performance Data. For purposes of comparison, select a given R value (resistance of radiant system and flooring goods)… lets say R-1. Follow that line down to 20 (btu/su/ft) output on the x axis and then straight down to the water temperature required to meet that load, at the bottom. The lower the temperature, the more efficient the system type.

This data is provided by the particular manufacture or from the Design Manual of Zurn Radiant, a leading manufacturer radiant tubing.

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